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81.
Toma LM Lescouëzec R Uriel S Llusar R Ruiz-Pérez C Vaissermann J Lloret F Julve M 《Dalton transactions (Cambridge, England : 2003)》2007,(33):3690-3698
The low-spin iron(III) complex AsPh(4)[Fe(III)(bpy)(CN)(4)].CH(3)CN (1) [AsPh(4) = tetraphenylarsonium cation] and the heterobimetallic chains [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)].4H(2)O with L = bpy (2) and phen (3) [bpy = 2,2'-bipyridine and phen = 1,10-phenanthroline] have been prepared and their structures determined by X-ray diffraction methods. The structure of 1 consists of mononuclear [Fe(bpy)(CN)(4)](-) anions, tetraphenylarsonium cations and acetonitrile molecules of crystallization. The iron(III) is hexacoordinated with two nitrogen atoms of the bidentate bpy and four carbon atoms of four terminal cyanide groups building a distorted octahedral surrounding around the metal atom. 2 and 3 are isomorphous compounds whose structure is made up of neutral 4,2-ribbon like bimetallic chains of formula [{Fe(III)(L)(CN)(4)}(2)Ni(II)(H(2)O)(2)] where the [Fe(III)(L)(CN)(4)](-) unit acts as a bis-monodentate bridging ligand toward the trans-diaquanickel(II) units through two of its four cyanide groups in cis positions. The chains exhibit two orientations in the unit cell and they interact with each other through hydrogen bonds involving the coordination and crystallization water molecules together with the uncoordinated cyanide nitrogen atoms of the [Fe(L)(CN)(4)](-) units. Compounds 2 and 3 behave as ferromagnetic Fe(III)(2)Ni(II) chains which interact ferromagnetically at very low temperatures in the case of 2, whereas metamagnetic-like behaviour is observed for with a critical field (H(c)) around 200 G. For H > H(c) the ferromagnetic Fe(III)(2)Ni(II) chains of 3 exhibit a frequency dependence of the out-of-phase ac susceptibility signal at T < 3.5 K. 相似文献
82.
Tadamasa Toma Yoshio Furuya Wataru Watanabe Kazuyoshi Itoh Junji Nishii Kenichi Hayashi 《Optical Review》2000,7(1):14-17
It is known that local refractive index change occurs when femtosecond laser pulses with extremely high peak power are launched into glass. We focused 130-femtosecond laser pulses of 800 nm into the bulk of glass and examined the shape of the induced refractive index change. We found that the length of the spot of the refractive index change along the optical axis reached about 30 μm despite the diameter being about 2 μm. To estimate the distribution of induced refractive index change, we fabricated Bragg grating by scanning the focused spot and calculated the amount of the change by applying Kogelnik’s coupled mode theory to the measured diffraction efficiencies of the higher order diffracted beams. 相似文献
83.
Shinobu Koda Masaki Miyamoto Maricela Toma Tatsuro Matsuoka Masahiro Maebayashi 《Ultrasonics sonochemistry》2009,16(5):655-659
This paper shows a systematic study of the 500 kHz frequency ultrasound efficiency on the microbial inactivation as a function of ultrasonic power delivered into the bacterial suspension. The inactivation of Escherichia coli IAM 12058, a Gram-negative bacterium and Streptococcus mutans JCM 5175, a Gram-positive bacterium is enhanced by increasing the ultrasonic power in the range of 1.7–12.4 W and the logarithm of survival ratio decreases linearly with irradiation time, except for E. coli sonicated with the highest power level. The rate constants were estimated in the linear region of the plots representing survival ratio logarithm vs. sonication time. A better understanding of the inactivation process at 500 kHz could be gained by suppressing the chemical effects with a radical scavenger. We find out that the rate constants increase with the ultrasonic power delivered into the solution and dramatically decrease by the addition of t-butanol as a radical scavenger to the bacterial suspension. For comparison, experiments were carried out at a low frequency level of 20 kHz. It was found out that for the same ultrasonic power delivered into the bacterial suspension, the inactivation was slightly enhanced at 500 kHz frequency. The examinations of bacterium performed with a TEM revealed lethal damages arising from the interaction of bacterial cells with the cavitational bubbles. A significant amount of empty cell envelopes as well as their cytoplasmatic content was detected. Thus, based on these new data, the mechanism of bacterial inactivation by ultrasounds at high frequency is discussed here. 相似文献
84.
Károly Lázár Andjelka Toma?evi? Goran Bo?kovi? Ern? Kiss 《Hyperfine Interactions》2009,192(1-3):23-29
Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a hematite/ZSM-5 composite is formed. The catalytic activity is attributed to iron located and stabilized in ionic dispersion. 相似文献
85.
C. Cristache K. Gméling O. Culicov M. V. Frontasyeva M. Toma O. G. Duliu 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(1):7-12
A comparative study performed by means of both epithermal neutron activation analysis (ENAA) and prompt gamma neutron activation
analysis (PGAA) concerning the distribution of 9 elements (Na, Al, Cl, K, Ca, Ti, Mn Fe and Sm) in unconsolidated sediments
collected from the Black Sea anoxic region is presented. Principal component analysis (PCA) was used as a supplementary method
in interpreting experimental data. The final results have shown that eight of them (Na, Al, Cl, K, Ti, Mn, Fe and Sm) have
concentrations which differ by less than 30% from the corresponding concentrations of Upper Continental Crust (UCC), confirming
the continental origin of sediments. At the same time, Ca concentration was about six times higher than that of UCC, this
significant enrichment being due to the presence of the neighbouring oxygenated zone of considerable deposits of shell debris,
characteristic of the Western Black Sea Continental Platform. Excepting Na and Mn, the concentrations of all other elements
involved in this intercomparison were coincident within one standard deviation which attests the accuracy of this test. At
the same time, PCA revealed the presence of five clusters, which could be put into concordance with the mineralogical composition
of sediments, each of them consisting in equal proportions of elements determined by both methods. 相似文献
86.
Abstract
Several achiral and chiral basic ionic liquids (ILs) were prepared and tested as the medium for Ru-catalyzed hydrogen-transfer reduction of different aromatic ketones. Hydrogen-transfer reduction of ketones proceeded well in achiral basic ILs using chiral catalysts. The interesting observation was made that raising the reaction temperature did not have a negative effect on enantioselectivity of the reaction. On the other hand no reaction was observed in chiral ILs. 相似文献87.
Dr. Régis Y. N. Gengler Prof. Dr. Dimitrios Gournis Akfiny H. Aimon Dr. Luminita M. Toma Prof. Dr. Petra Rudolf 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(24):7594-7600
Much of the research effort concerning the nanoscopic properties of clays has focused on its mechanical applications, for example, as nanofillers for polymer reinforcement. To broaden the horizon of what is possible by exploiting the richness of clays in nanoscience, herein we report a bottom‐up approach for the production of hybrid materials in which clays act as the structure‐directing interface and reaction media. This new method, which combines self‐assembly with the Langmuir–Schaefer technique, uses the clay nanosheets as a template for the grafting of C60 into a bi‐dimensional array, and allows for perfect layer‐by‐layer growth with control at the molecular level. In contrast to the more‐common growth of C60 arrays through nanopatterning, our approach can be performed under atmospheric conditions, can be upscaled to areas of tenths of cm2, and can be applied to almost any hydrophobic substrate. Herein, we report a detailed study of this approach by using temperature‐dependent X‐ray diffraction, spectroscopic measurements, and STM. 相似文献
88.
Polar and longitudinal magnetooptical Kerr effects in magnetic film/spacer/magnetic substrate system
Š. Višňovský J. Gřondilová J. Hamrle R. Lopušník N. Keller 《Czechoslovak Journal of Physics》2001,51(11):1215-1228
The paper deals with the electromagnetic theory of longitudinal and normal incidence polar magnetooptical Kerr effects (MOKE)
in sandwich structures consisting of a magnetic film on a thick magnetic substrate separated by a nonmagnetic spacer. These
structures are employed in fundamental studies of magnetic exchange coupling, tunnel magnetoresistance, spin polarized current,etc., as well as in the design of the magnetoelectronic devices,e.g., magnetic random access memories. The results are expressed in terms of the Jones reflection matrix. This makes the analysis
of the observed MOKE in various experimental set-ups easier. To first order in off-diagonal elements of the permittivity tensor,
the analytical expressions approximate the results obtained using rigorous matrix formalisms with a little loss in accuracy,
provided the magnetooptical effects quadratic in the offdiagonal elements are negligible. The total MOKE is expressed as a
a sum of components originating from magnetic film and magnetic substrate, respectively. The components enter the analytical
expressions with different phases and may be identified separately by a proper control of the polarization state and photon
energy of the incident radiation, angle of incidence, nonmagnetic spacer thickness, and radiation wavelength. The formulae
are derived without any restriction on the magnetic film thickness. However, for a rapid evaluation of the trends the MOKE
response is also treated under the assumption that the thickness of the magnetic film is much smaller than the radiation wavelength.
This work has been partially supported by Grant Agency of the Czech Republic (#202/97/1180 and #202/00/0761), Barrande Project
and Grant Agency of Charles University. 相似文献
89.
Magneto-optic (MO) effects in magnetic multilayers with periodic regions are discussed assuming normal incidence of polarized
waves and polar magnetization (Faraday and polar Kerr effects). From the (4 × 4)-matrix formalism simplified analytical expressions
linear in the off-diagonal permittivity tensor element are obtained with no loss in accuracy. The MO effects are expressed
as weighted sums of contributions from individual layers. Approximate expressions are given for the case when the thickness
of magnetic layers is much smaller than the radiation wavelength. The procedure is illustrated on superlattices consisting
of symmetric sandwiches of ultrathin magnetic and non-magnetic metallic layers.
Partial support from the Grant Agency of Czech Republic # 202/00/0761 is acknowledged. 相似文献
90.
Résumé. Nous montrons qu'une surface de la classe VII0 avec b
2 > 0 sur laquelle existe un champ de vecteurs non trivial contient exactement b
2 courbes rationnelles. Il s'ensuit par un théorème de I. Nakamura qu'une telle surface se déforme en une surface de Hopf primaire
éclatée. Ce résultat contribue ? la classification des surfaces complexes compactes avec champs de vecteurs.
Received: August 6, 1998 相似文献